A number of different automated clinical chemical analyzers are known in the art. Such analyzers range from simple, largely manually operated instruments to highly complex, nearly fully automated instruments. Each analyzer has its own particular performance characteristics related to the number ("menu") of different tests that the analyzer can perform and the number of samples that can be processed in a given period of time ("throughput").
Large scale, highly complex analyzers useful in large hospitals and clinical laboratories have been developed which have both a large menu of tests which the instrument can perform and a high throughput. Such an analyzer is described in U.S. Pat. No. 4,965,049 issued to Lillig et al. which is incorporated herein by reference in its entirety.
Most such large scale, highly complex analyzers employ liquid extraction and discharge equipment comprising hollow open-ended extraction/discharge probes operatively connected to sources of vacuum and pressure. Such probes can be conveniently used to extract a predetermined quantity of liquid from one container within the analyzer and deposit that liquid into another container within the analyzer. In a typical configuration, the sources of vacuum and pressure are syringe-type pumps which alternatively push or pull a carrier liquid toward the probes or away from the probes.
In such configurations, problems arise within the analyzers when solid materials, such as dried chemicals or foreign materials obstruct the lines carrying the carrier liquid to the extraction/discharge probes. Such obstructions affect the extraction and discharge functions of the probe and can therefore seriously affect the efficiency of the analyzer and/or the quality of the analyses performed by the analyzer. Accordingly, such obstructions need to be identified immediately when they occur.
Several obstruction detection methods have been proposed. One of the most sophisticated uses a transducer to continuously monitor pressure within the carrier liquid lines. Unfortunately, even this sophisticated detection method has not been fully satisfactory. Specifically, the transducers have not been able to monitor pressures within the carrier liquid lines with sufficient accuracy. This is because prior art configurations operatively connect the transducer to the carrier liquid lines using an intermediary conduit which may be filled with air, carrier liquid or some other non-flowing fluid. Such intermediary conduits delay and dampen pressure transmissions from the flowing carrier liquids to the transducer. Also, the intermediary conduits tend to become clogged with foreign material.
Apart from these problems with the intermediary conduits, dissolved gases within prior art configurations tend to also delay and dampen pressure transmissions from the flowing carrier liquid to the transducer.
Accordingly, there is a need for an obstruction detection apparatus which can efficiently detect obstructions within the pressure/vacuum lines of automated chemical analyzers with a high degree of accuracy.